The present invention relates to an improved hand operated offset shears or snips which can be used for cutting sheet metal or similar material in either a straight line or in a right or left hand direction, including circle cuts down to an opposing circle of about 2.0" to 2.5" in diameter.
When sheet metal or similar material is cut with conventional snips, one or both edges of the cut sheet material may interfere with the body of the snips, making it difficult to advance the snips into the sheet material and distorting the cut edges. This interference is greatest when cutting irregular shapes, particularly sharp curves and especially small circles. Accordingly, conventional snips are often supplied in mirror image configurations particularly adapted for either left-hand or right-hand turning cuts. Also, when conventional snips are used to cut thick, tough or stiff material, the sheet material may tend to slide away from the blades as they are closed, decreasing the efficiency of the cutting. Further, conventional snips may require long handles and substantial force to be exerted by the operator in order to cut many sheet materials.
As illustrated by U.S. Pat. No. 2,264,840, one approach to decreasing the interference of the cut sheet material with the body of the snips is to offset the cutting surfaces with respect to the shank portions of the snips such that the cut sheet material passes to one side of the shank portions. Also illustrated therein is the practice of extending the cutting blades laterally approximately at right angles to the place of operation of the shanks. This configuration facilitates the advancement of the snips into the sheet material by reducing the extent to which the cut sheet material must be spread vertically to pass above and below the lower blade, thereby decreasing the tendency of the sheet material to slide away from the cutting surfaces. More recently, a link arrangement, as shown in U.S. Pat. No. 3,587,173, has been proposed to reduce the force required by the operator to cut heavy sheet materials.
As with conventional snips, most available offset snips generally can be used only in cutting curves either in the left-hand or right-hand direction, thus requiring other offset snips having a mirror image configuration when curves must be made in the other direction. Also, the laterally extending blades of available offset snips must be carefully ground and aligned during manufacture and, generally, cannot be conveniently reground if they become dull or damaged. Abuse of the blades by cutting wire or similar materials may render the snips useless for cutting sheet material. Accordingly, a need exists for improved offset snips which can be easily resharpened if the blades become dull or damaged, and which embodies a pinch or shear type wire cutter. Further, there is a need for an improved handle and toggle arrangement or configuration making the offset snips more powerful and convenient to use when cutting heaving sheet material.
In applicant's related U.S. patent application, a pinch type cutter is employed where part of the upper blade member serves as the anvil and a portion of the lower blade member serves as the chisel for the wire cutter. With such an arrangement, a "relief" formed at the base of the cutter elements, due to the manufacturing processes involved, requires wire that is to be cut to be specifically positioned substantially centrally in the cutter. Should, for example, a small diameter wire be positioned at the base of the cutter, the "relief" in effect precludes the wire from being cut by the chisel and anvil. This "relief" is created as a result of the various grinding operations or passes required in order to grind the opposite faces of the chisel. Also, in the formation of the chisel of such related patent application, the grinding passes generally create a broad V-shaped chisel having an angle between the sides thereof of about 70 degrees. Such an angular chisel configuration, although adequate for most applications, requires more difficult manufacturing processes to fabricate resulting in considerably higher product cost. It also requires higher pressures and forces to cut wire as the chisel has a broader cutting angle and wire of smaller and even larger gauges can easily become snagged or trapped at the base of the cutter in the "relief" area. Such an occurrence then makes it difficult to cut the wire and one must manually reposition the wire centrally so that the chisel cuts or pinches across the full width of the wire with the wire trapped squarely between the anvil and full face width of the chisel.
Another disadvantage of applicant's related patent application is the fact that the lower blade member, although offset, does not provide adequate clearance so that very small opposing diameter circle cuts cannot be made. This deficiency makes it necessary to fabricate and stock both left and right hand cutters as neither offset snips is truly considered an all-way or universal type of snips capable of cutting in any direction, that is, straight, right-hand and left-hand. It should be recognized that for most applications, cutting arcs, curves, or circles down to at least about 2.0" to 2.5" in diameter would satisfy most field requirements of the tool.
It is therefore an object of the present invention to provide improved all-way offset snips which can cut sheet material in both left-hand and right-hand curves, as well as in very small diameter circles, without being impeded by interference of the cut material with the body of the snips.
It is a further object of the present invention to provide improved all-way offset snips of increased power and in which the cutting surfaces may be conveniently and economically resharpened if the cutting surfaces become dull or damaged, and resharpening of the chisel of the wire cutter can be done by a single grinding pass with the boss of its blade member.
It is a further object of the present invention to provide improved all-way offset snips having either pinch or shearing means for cutting wire and the like, thereby eliminating the need for a second tool and reducing the abuse of the sheet material cutting surfaces of the offset blade members.
It is a further object of the present invention to provide improved all-way offset snips having substantially increased power due to a toggle arrangement which provides greater force action to the central toggle pivot of a dual link/three pivot point toggle linkage because of the general linearity of the toggle pivot points when the offset snips is in closed position.
It is still a further object of the present invention to provide an "all-way" offset snips having handles with a toggle linking arrangement of considerably greater power which can more easily be grasped when the snips are in the open position and more easily forced to the closed position.
It is yet another object of the present invention to provide an all-way offset snips having either a pinch or shear type cutter, with the anvil portion of the pinch cutter on the upper blade member and the chisel on the lower blade member regardless of the type of cutter which is employed.
It is still yet another object of the present invention to provide an all-way offset snips having a chisel which can be sharpened in a single grinding pass with the boss of its blade member and which cuts across the full width of the anvil.